Intramolecular PIFA-Mediated Alkyne Amidation and Carboxylation Reaction

Abstract

The hypervalent iodine reagent PIFA promotes the intramolecular electrophilic cyclization of easily accessible alkynylamides and alkynyl carboxylic acids, leading to the formation of pyrrolidinone and lactone skeletons, respectively, in a very efficient way. A synthetic study and a mechanistic proposal for these transformations are presented.

Cycloisomerization of Acetylenic Acids to γ-Alkylidene Lactones using a Palladium(II) Catalyst Supported on Amino-Functionalized Siliceous Mesocellular Foam

“…The reaction mixture was acidified to pH 2 using 2M aqueous HCl and extracted with Ethyl-4-pentynoate was prepared following reported procedures. 39 …”

Synthesis of α-Acyloxyketone Derivatives <i>via</i> the Platinum-Catalyzed Migration of Propargylic Esters

“…To determine the effect of the electronic state of the ester of the outcome of the reaction, we also investigated several non-and monosubstituted benzoyl groups. The results of these reactions revealed that the use of an aromatic ring bearing an electronwithdrawing group gave a better yield than an aromatic ring bearing an electron-donating group or no substituent at all ( Table 2, entries [15][16][17].…”

“…[9][10][11] Based on the importance of α-acyloxyketones to chemistry, the development of a concise synthetic method for the preparation of α-acyloxyketone derivatives is important. Although a wide variety of synthetic methods have been investigated to date, 12,13) reports pertaining to the direct synthesis of α-acyloxyketone III by the oxidation of alkyne I are rare, most likely because of the difficulties associated with suppressing the over-oxidation of the product and controlling the regioselectivity of the reaction [14][15][16] (Chart 1). To allow for the direct synthesis of α-acyloxyketone III from alkyne I, several researchers directed their attention towards the transition metal-catalyzed migration of propargylic esters [17][18][19][20] to affect a facile oxidative transformation.…”

Metal-free syntheses of oxazoles and their analogues based on λ3-iodane-mediated cycloisomerization/functionalization reactions or [2+2+1] cycloaddition type reactions

“…6,7 Therefore, directed toward the development of the metal-free cycloisomerization/functionalization sequence of N-propargyl amides, we have focused on the activation mechanism by PIFA and the reductive elimination of iodobenzene (Scheme 2). 4 Thus, the similar properties of λ 3 -iodane to metal catalyst would be expected to lead to the metal-free formation of oxazoles concomitant with the introduction of oxygen functional groups.…”

“…In addition to the abovementioned reactions, Tellitu and Domínguez's group have reported that phenyliodine(III) bis(trifluoroacetate) (PIFA) directly promote the oxidative cyclization of 4-alkynylcarboxamides (Scheme 2). 4 In this procedure, PIFA works not only as a donor of oxygen function group but also as an activator for the triple bond (R' = alkyl). However, the similar approach to the aromatic heterocycles by λ 3 -iodanes had not been reported, although oxidative cycloisomerization of enynols by 2-Iodoxybenzoic Acid (IBX) had been known as the facile synthesis of 2-acylfurans.…”